1. Field of the Invention
The present invention relates to a blind fastener setting device having a drawing mechanism and an adjustably supported tip piece that has several mandrel guide channels, each of which can be aligned with respect to the drawing mechanism.
2. Discussion of the Related Art
Blind rivets and blind rivet nuts are set by a blind fastener setting device. The most commonly used rivet dimensions today lie between 2 and 5 mm in diameter, and are made of various materials. The diameter of the rivet mandrels, which are designed to break off at a predetermined breaking point when the required setting force has been reached, have diameters between 1.5 and 3.2 mm. Because of these varying diameters, the tip pieces on which the rivet heads are supported during setting are matched to the rivet mandrel diameter. Thus, the bores of the tip pieces that are used for the most commonly used rivets lie in the range from 1.9 to 3.6 mm. If the bore or the mandrel guide channel is too small, that mandrel guide cannot work with larger rivets because the thicker mandrels will not fit into the tip piece. If, on the other hand, the mandrel guide has a bore that is too large, thinner mandrels will fit into the tip piece, but working with the thinner blind rivet is still problematical. For example, the mandrel can be pulled all the way through the rivet without any breaking off occurring. Additionally, visible ring-shaped impressions and deformations can occur because the necessary supporting surface is not present. Therefore, the tip piece must always be chosen so that it matches the rivet size that is being used.
As a result, most setting devices are provided with exchangeable tip pieces. However, a tool is usually required to change the tip piece. The number of working steps involved in changing a rivet size is substantial. To exchange a tip piece, the tip piece must be removed by using the tool, a matching tip piece must be sought out, and then installed by once again using the tool. The tip piece that was removed must then be properly placed so that it will not be lost. As a result, for applications in which a frequent changing of rivet sizes is necessary, the required equipment preparation time takes on considerable dimensions.
U.S. Pat. No. 4,648,259 to Pendleton discloses an adjustable tip piece for blind rivet setting devices. The tip piece includes two jaws. Each jaw has a triangular recess so that the jaws, which lie opposite each other, together form a mandrel guide channel that is approximately rectangular or square in cross-section. The two jaws taper down to a point. With the aid of a union nut, the jaws can, by tilting, be brought towards each other in the region of the tip piece. If a larger diameter mandrel guide channel is used, a slot is created between the two jaws. If a smaller diameter mandrel guide channel is used, the two supporting surfaces, which are arranged in a coplanar fashion when the diameter is larger, are disposed at an angle to the head of the rivet, which leads to visible impressions on the head of the rivet, and to a reduction of the setting ability.
EP 0 173 817 A1 discloses a blind fastener setting device, where the tip piece can be rotated around an axis that encloses an angle of approximately 45.degree. to the drawing direction of the drawing mechanism. Thus, the mandrel guide channels are inclined at this angle with respect to the axis. By rotating the tip piece around the axis, the individual mandrel guide channels can be brought into alignment with the drawing mechanism. A disadvantage with this design is that the tip piece and the housing have a relatively high manufacturing expense. In addition, the housing must be of a relatively large overall size, and the diameter of the housing in particular must be made correspondingly large. The larger size of the housing makes the device heavy and unwieldy. In many cases, rivets are required which have rivet mandrels with excessive lengths so that the drawing mechanism can grip the mandrel, which is fed through the tip piece and the necessary parts of the housing.